The spread of personal computers and workstations has led to the development of networks for interconnecting such equipment and common resources such as printers and data storage devices. More powerful and sophisticated computing equipment and programs have progressively become available, allowing the processing of data in larger and larger quantities, for example in the form of database information and graphic images. These developments have in turn placed increasing demands on the speed and capacity of networks.
Various new networking technologies have been proposed to cater for these demands. One such technology is the fibre distributed data interface (FDDI), which is based on the use of optical fibres and optical signals. However, practical experience has shown that although this technology can provide the required performance, it is relatively expensive, requiring the costly process of installing complete new networks of optical fibre, which is itself inherently expensive.
Accordingly attention has also been directed to the possibility of transferring data at high speed over existing wiring installations, thereby avoiding the cost of installing a new network and gaining additional return for the expense previously incurred in installing the existing wiring.
One possible technique along these lines involves the use of unshielded twisted-pair (UTP) telephone cables of the kind already used for lower-speed local-area networks. In this technique, described for example in U.S. Pat. No. 5,119,402, the required high data rate is achieved by transferring the data over multiple conductors, so that different portions of the data are transmitted simultaneously over respective conductors.
In data communication systems it is desirable to ensure a high degree of error detection. One particular class of errors is those affecting individual, spaced bits. Such errors are known as single-bit errors. Various techniques have been developed for the detection of single-bit errors, including cyclic redundancy check (CRC) codes and the encoding of data values using a limited number of valid code words. However, there remain certain combinations of single-bit errors which such techniques may not detect.
It is an object of this invention to provide a method and system for communicating data, for example using cables with multiple conductors, which facilitates the detection of single-bit errors.